Clonal variation of wood density variables in Pinus radiata

Wood basic density was assessed on cuttings from 11 clones in a 16-year-old clonal trial of Pinus radiata D. Don, using breast-height increment cores, and wood disc samples from the butt, breast height (1.4 m), 6, 11, 16, and 20 m height. The cuttings came from 5-year-old trees, and were thus physiologically "aged". The sample clones were chosen from the 120 clones in the trial, to cover the available range of wood density and tracheid length. Tree average wood density values were calculated from gravimetric measurements on the discs and within-tree trends were assessed using a scanning X-ray densitometer. There were significant differences among clones, among trees within clones, among rings, and in interaction between rings and clones. The effects of clones and rings were dominant. There were also significant differences in pith-to-bark trends among clones, and in height up the stem at a given ring number from the pith in half of the clones. There were significant differences in the breast-height ring density profile between ring groups 1-5 and 11-15 due to increases in overall density, and in the amount and density of